IJPSR (2016), Vol. 7, Issue 6 (Research Article) Received on 29 December, 2015; received in revised form, 03 February, 2016; accepted, 03 April, 2016; published 01 June, 2016 RP-HPLC METHOD DEVELOPMENT AND VALIDATION OF STABILITY INDICATING METHOD A FOR ESTIMATION OF LOSARTAN POTASSIUM UNDER STRESS CONDITION AND TABLET DOSAGE FORM Amna B.W.E Mohammed 1* and Elsadig H.Rudwan 2 College of Animal Production science and Technology 1, Sudan University of Science and Technology, Sudan Amipharma Laboratories Ltd 2, Khartoum, Sudan Key words: Losartan potassium, RP-HPLC, experimental design, Tablet, ICH guideline. Correspondence to Author: Amna B.W.E Mohammed College of Animal Production science and Technology, Sudan University of Science and Technology, Sudan Email: ehrrajab@hotmail.com ABSTRACT: Losartan potassium, a highly effective blood pressure lowering agent, has widely used for treatment of hypertension. Simple, economic, selective, and precise and stability indicating HPLC method has been developed and validated for analysis of losartan potassium in bulk drug and formulation dosage form. In order to optimize more one response at time, the chemo metric approach which includes 2 3 factorial design at two level with three factors was set up to standardize the chromatographic condition. The mobile phase was 40:60 ACN: Buffer consist of 0.05% of orthophosphoric acid and 0.05% Triethylamine at flow rate 1.0ml/minute the eluent was monitored at 225nm. The calibration plots constructed using the concentration of 6.4 to 9.6µg/ml (80-120%) with r 2 =0.999, recovery =99.44% was indicative of accuracy of proposed method. The precision was calculated as repeatability, intraday (RSD) for the drug. INTRODUCTION: Losartan potassium is chemically: 2-butyl-4-chloro-1-[[2 -(1H-tetrazol-5- yl) [1, 1 -biphenyl]-4-yl] methyl]-1h-imidazole-5- methanol monopotassium salt. Losartan is a phenyl tetrazole substituted imidazole compound which acts as a selective, angiotensin II receptor type I antagonist and is employed in the management of essential hypertension 1. Method validation study include system suitability, linearity, precision, accuracy, specificity, robustness, limit of detection, limit of quantification and stability of sample, reagents, instruments. The aim of this investigation was to establishing a new simple and sensitive method that could be used in analysis degradation products of Losartan potassium. QUICK RESPONSE CODE DOI: 10.13040/IJPSR.0975-8232.7(6).2343-51 Article can be accessed online on: www.ijpsr.com DOI link: http://dx.doi.org/10.13040/ijpsr.0975-8232.7 (6).2343-51 FIG.1: LOSARTAN POTASSIUM International Journal of Pharmaceutical Sciences and Research 2343
Several analytical methods have been applied to the analysis of Losartan potassium in pharmaceutical products that make use of high performance thin layer chromatography (HPTLC, capillary electrophoresis (CE), capillary electro chromatography (CEC and spectrophotometry. The literature reports many analytical methods for the quantitation of Losartan in tablets using HPLC. The USP describes an RP-HPLC method for the determination of LOP in tablets MATREIAL AND METHODS: All chemicals and reagents used in the present study were Anal R grade and solvents were of HPLC. To attain high accuracy and reliability of results of the research work. The commercial tablets of losartan potassium are procured from local market, the details of procured materials are shown in Table 1 and the details of instruments used are shown in Table 2. TABLE1: DRUG AND CHEMICAL PROCURED AND USED FOR THE PRESENT STUDY S.no Material Procured from 1 Losartan potassium working standard 99.86% HUNHN Pharmaceutical CO.Ltd China 2 Acetonitrile HPLC grade Merck pharmaceutical India 3 Methanol HPLC grade Merck pharmaceutical India 4 Water HPLC grade Merck pharmaceutical India 5 O-phosphoric acid S.D fine Chem ltd India 6 Triethylamine HPLC grade S.D fine Chem ltd India TABLE 2: INSTRUMENT USED FOR PRESENT STUDY S.no Name of instrument Model Manufacturer 1 Digital balance sartorius CP2245 Germany 2 Ultrasonic bath sonicator M0109 INDIA 3 ph meter MI180 U.K 4 Spectrophotometer UV-1800 JAPAN 5 HPLC SYKAM S3210 Germany 6 Stability Chamber INDIA 7 Water bath Type1083 Germany Preparation of Standard: Preparation of standard losartan potassium solution 109.26 mg of losartan potassium working standard 99.86% weighed and dissolve in dry clean 100ml volumetric flask, add 50 ml of methanol sounicate for 15 min in ultrasonic the volume completed to the mark to final obtained 1mg/ml stock solution. Series of five standard solution in the separate concentration range of 6.4 to 9.6 µg/ml were prepared by dilution with diluent. Preparation of diluent: 9:1 of Acetonitrile and water. Preparation of Sample: 20 tablets of losartan potassium was poured in a mortar and thoroughly ground into fine powder. Out of this tablet powder equivalent to 100mg of losartan potassium was taken and dissolved in 100ml volumetric flask 50 ml of methanol added, sonicate for 15min complete the volume to the mark, filtrate through 0.45µm filter and the same solution was further diluted stepwise with diluent to have a concentration 8µg/ml. Preparation of solutions for degradation studies Acid and base degradation: Accurately weight 54.63mg of losartan potassium and transferred into 100 volumetric flask, to it 10ml of methanol was added and sonicateted for 15 minutes with intermittent shaking. To it 5 ml of 0.1M of HCl was added and 5ml of 0.1M NaOH were added separately. The sample was heated on boiling water bath for 45 minutes, cool to room temperature and diluted to volume with diluent the sample was neutralized to ph 7 by adding 0.1M HCl or 0.1 M NaOH, mixed well. The acidic degradation and the alkaline forced degradation was performed in dark in order to exclude the possible degradation effect of light. This solution was filtered through 0.45um filter, 5ml of the filtrate was transferred to 25 ml volumetric flask, diluted to volume with diluent(9:1) acetonitrile International Journal of Pharmaceutical Sciences and Research 2344
and water, mixed well and injected into the HPLC system. Oxidation degradation: Accurately weight 54.63mg of losartan potassium and transferred into 100 volumetric flask, to it 10ml of methanol was added and sonicateted for 15 minutes with intermittent shaking. To it 5 ml of 3% H 2 O 2 was added. The sample was heated on boiling water bath for 45 minutes, cool to room temperature and diluted to volume with diluent, mixed well. This solution was filtered through 0.45um filter, 5ml of the filtrate was transferred to 25 ml volumetric flask, diluted to volume with diluent (9:1) acetonitrile and water, mixed well and injected into the HPLC system. Thermal degradation: Accurately weight 54.63mg of losartan potassium and transferred into 100 volumetric flask, to it 10ml of methanol was added and sonicateted for 15 minutes with intermittent shaking.the sample was heated on boiling water bath for 45 minutes, cool to room temperature and diluted to volume with diluent, mixed well. This solution was filtered through 0.45um filter, 5ml of the filtrate was transferred to 25 ml volumetric flask, diluted to volume with diluent(9:1) acetonitrile and water, mixed well and injected into the HPLC system. Photolytic degradation: Accurately weight 54.63mg of losartan potassium and transferred into 100 volumetric flask, to it 10ml of methanol was added and sonicateted for 15 minutes with intermittent shaking. Kept in UV 254nm (UV radiation for 16 hours), completed to the mark with diluent. This solution was filtered through 0.45um filter, 5ml of the filtrate was transferred to 25 ml volumetric flask, diluted to volume with diluent (9:1) acetonitrile and water, mixed well and injected into the HPLC system. RESULTS: Selection of detection wavelength: To a chief goal of this study was to develop a rapid RP-HPLC method for the determination of losartan potassium in bulk drug and tablet formulation by utilizing most commonly column C 18 with Ultraviolet detection at wavelength 225nm. By using UV spectrophotometer the losartan potassium was scanned in the region of 200-400 nm in spectrum mode, the outcome absorption 225nm Fig.1 FIG.2: FIRST DERIVATIVE SPECTRUM OF LOSARTAN POTASSIUM.ID 225NM Optimization and method development: The main intention of method development is that all required chromatographic conditions are inevitably optimized. The traditional approach to HPLC optimization is to perform an experiment by trial and error or by change one control variable at time; such method can frequently require a very large number of International Journal of Pharmaceutical Sciences and Research 2345
experiments to identify the optimal condition. Recently computer assessed to HPLC separation has addressed the problem using factorial design strategies. In this work a three factors with two level was applied to predict the retention behavior of Losartan potassium and optimize their isocratic elution using acetonitrile as organic modifier and buffer as mobile phase. The goal of this investigation was to establishing a new simple and sensitive method that could be used in analysis degradation products of Losartan potassium. TABLE 3: MATRIX FOR THREE FACTORS (NUMBER OF RUNS =8) Experiment Factor X1 Factor X2 Factor X3 Run1-1 -1-1 Run2 1-1 -1 Run3-1 1-1 Run4 1 1-1 Run5-1 -1 1 Run6 1-1 1 Run7-1 1 1 Run8 1 1 1 TABLE 4: CHROMATOGRAPHIC CONDITION EMPLOYED AS PER 2 3 FACTORIAL DESIGN Factors Response Peak. area Run t R Total plate asym5% X1 X2 X3 Run1 40 35 1.0 4.40 4767 1.38 563.4 Run 2 60 35 1.0 3.316 4477 1.5 558.35 Run 3 40 40 10 9.45 5497 1.24 542.16 Run 4 60 40 1.0 9.533 5594 1.19 540.06 Run 5 40 35 1.4 6.816 4728 1.23 381.56 Run 6 60 35 1.4 2.383 2312 1.40 416.18 Run 7 40 40 1.4 3.10 2995 1.14 393.75 Run 8 60 40 1.4 6.766 5403 1.33 387.96 X2 and X3 factors are represent, Acetonitrile, Buffer and low rate (-) and (+) represent the low and high of acetonitrile, buffer and flow rate. Standard regression curve analysis was performed by used IPM SPSS software version 22and minitab17 and prism 6.07. coefficients between,x1, X2 and X3 stand for the main effect, X1X2, X2X3 and X1X3 are the two way interaction between the main effect and X1X2X3 is the three way interaction between the main effect 2, 3. The model summary indicate that the model was fit, R 2 =0.9961 and standard error of estimation was 0.1776%., this for dependent variable: retention time. The obtained adjusted R 2 were within acceptable limit of R 2 0.80, indicating that the experimental data were a good fit to the equation: Y = ß 0 +β 1 X 1 +β 2 X 2 +β 3 X 3 +β 4 X 1 X 2 +β 5 X 2 X 3 + β 6 X 1 X 3 +β 7 X 1 X 2 X 3 Where Y is the level of the measured response, ß 0 is the intercept, ß 1 to ß 7 are the regression FIG.3: INTERACTION PLOT SHOWING THE INFLUENCE OF RETENTION TIME International Journal of Pharmaceutical Sciences and Research 2346
standard solution 8µg/ml was injected to check system suitability. FIG. 4: STANDARDIZED EFFECT SHOWING THE INFLUENCE OF RETENTION TIME For pharmaceutical formulation: Twenty tablets of losartan potassium 50mg was put into mortar and crouched to smooth powder. From this grounded tablet powder; equivalent to 50mg of losartan potassium was accurately and diluted with methanol sonicated for 15 min then the Solution was filtered through 0.45 µm membrane filter to have a concentration 8µg/ml,. The results of assay in respect of the proposed method are mentioned in Tanle15. Method validation: 4. According to guideline of ICH Q2 (R1) all parameters as discussed below were analyzed and validated accurately following the procedure of proposed method. FIG.5: MAIN EFFECT SHOWING THE INFLUENCE OF RETENTION TIME TABLE 5: OPTIMIZED CHROMATOGRAPHIC FOR THE PROPOSED METHOD Parameter Mobile phase Flow rate Wavelength Injection volume Column Column temperature Run time Retention time Condition used for analysis Acetonitrile,0.05% orthophosphoric acid+0.05% triethylamine ( 40:60 v/v) 1.0 ml/min 225 nm 20µl loop C 18 (250x4.6 mm,5µmm) Ambient 20min 10 min After close observation of the concerned parameters based on the detailed results obtained and discussions of this part the following procedures were recommended for deciding losartan potassium in bulk samples as pharmaceutical formulation. For bulk samples: To get a stable base line the HPLC system was stabilized for 40 minutes subject to the chromatographic conditions describe in Table 2. One blank followed by 6 replicates of a single System suitability: During analytical method development system suitability test give an added level of confidence that the accurate mobile phase, flow rate, temperature, and column were used which ensures the system performance (pump and detector) where in parameters of system suitability such as retention time, resolution, efficiency (number of theoretical plate) and tailing factor are involved and they should be within the defined limits. The results of system suitability in respect to the proposed method are mentioned in Table 6. TABLE 6: SYSTEM SUITABILITY RESULTS FOR THE PROPOSED METHOD S.no Parameters Results * 1 Retention time 9.98 minutes 2 Theoretical plate 3837 3 Theoretical plate per 0.065 meter(t.p/m) 4 Asymmetry 5% 1.1 5 Resolution - * Results for triplicate value (n =3) Specificity: The excipients in tablets contained the following in active ingredients: Microcrystalline cellulose, lactose, maize starch and magnesium stearate as excipients, chromatograms showed that no excipients interfered with losartan potassium peak Fig.8. International Journal of Pharmaceutical Sciences and Research 2347
The linearity for HPLC method was determined at five concentration levels ranging from 6.4-9.6 μg/ml for Losartan potassium the calibration curve was constructed by plotting response factor against respective concentration of Losartan potassium. The method of least square analysis was performed to obtain slope, intercept and correlation coefficient value. Figure. Shows the calibration curve of losartan potassium. TABLE 8: LINEARITY DATA OF LOSARTAN POTASSIUM FIG. 7: ACID DEGRADATION OF LOSARTAN POTASSIUM Level method% 80 80 80 90 90 90 100 100 100 110 110 110 120 120 120 Peak area at 225nm 399.6630 398.956 401.1640 463.0825 459.1520 456.3130 504.380 503.350 504.140 556.816 548.022 552.9085 600.7550 597.909 594.933 Actual % RSD % 79.30 79.16 79.60 91.89 91.11 90.54 100.07 99.88 100.04 110.48 109.00 110.00 119.2 119.00 118.00 0.28 0.74 0.10 0.68 0.54 Limit NMT 2% FIG.8: HPLC CHROMATOGRAM OF LOSARTAN POTASSIUM WORKING STANDARD Stress testing of losartan potassium: Under acidic condition losartan potassium was degradated up to 0.7 %.Under alkali stress losartan potassium was degradated up to 1.63 %. Only small percent of degradation occurred in UV radiation and oxidation, degradated up to 1.87 under thermal condition. TABLE 7: PERCENTAGE OF DEGRADATION S.n o Condition 1 No stress treatment(control sample) % Assay of Losartan potassium % degradation 99.88 Nil 2 Acid 99.17 0.70 3 Alkali 98.25 1.63 4 H 2 O 2 99.31 0.57 5 UV 99.84 0.37 6 Thermal 98.01 1.87 FIG.9: LINEARITY CURVE OF LOSARTAN POTASSIUM TABLE 9: REGRESSION ANALYSIS DATA OF LOSARTAN POTASSIUM Parameters Results Linear range 6.4-9.6µg/ml Regression equation(y=a+bx) y = 0.996x + 0.215 Correlation coefficient(r 2 ) 0.9996 Slope ( b) 0.996 Intercept ( a) 0.215 Standard deviation of slope(s b ) 0.009 Standard deviation of intercept(s a ) 0.845 Standard error of estimation 0.88509 The precision (system method) of the proposed method was evaluated by carrying out six International Journal of Pharmaceutical Sciences and Research 2348
independent assays of test sample. RSD (%) of six assay value obtained was calculated. The intermediate precision was carry out by analyzing the sample in different days. TABLE 10: INTRA-DAY PRECISION RESULT OF LOSARTAN POTASSIUM Repeatability precision Injection Peak area Assay Sample Concentration no ( mv.s) 1 237.66 100.22 Losartan potassium 8µg/ml 2 236.12 99.60 3 238.70 100.65 4 235.77 99.42 5 236.63 99.80 6 236.81 99.86 % RSD N=6 0.44 TABLE 11: INTER-DAY PRECISION RESULT OF LOSARTAN POTASSIUM Intermediate precision Injection no Peak area( mv.s) Assay % RSD Sample Concentration N=6 1 238.54 100.62 Losartan 8µg/ml 2 236.66 99.83 0.43 potassium 3 237.26 100.10 4 236.19 99.63 5 235.94 99.52 6 235.78 99.46 Accuracy (recovery studies) The accuracy of the HPLC method was confirmed by recovery studies by spiking 80,100 and 120% of pure drugs to the pre analysed samples and the samples after dilution injected into the system (n=3). The peak area of each drug was measured and recovery data for losartan potassium given in Table 12. TABLE12: RECOVERY RESULTS OF LOSARTAN POTASSIUM Amount added µg/ml Amount found µg/ml Recovery% Statistical analysis of % recovery 6.4 6.34 99.06 MEAN 99.15 6.4 6.33 99.0 SD 0.17 6.4 6.36 99.4 %RSD 0.22 8.0 8..05 100.62 MEAN 100.22 8.0 8.00 100.00 SD 0.28 8.0 8.004 100.05 %RSD 0.34 9.6 9.54 99.37 MEAN 98.96 9.6 9.52 99.17 SD 0.45 9.6 9.44 98.33 %RSD 0.55 Robustness: Robustness of the method was determined by small deliberate changes in flow rate, and wavelength. The content of the drug was not adversely affected by these changes as evident from the low value of relative standard deviation indicating that the method was rugged and robust. TABLE 13: CHANGE OF FLOW RATE Flow rate(ml/min) Mean area ±SD SEM Mean t R ±SD % Bias % RSD Original Used Level N= 3 0.95-0.05 227.27±1.81 1.28 10.12±0.097 0.0173 0.097 1.0 1.0 0 213.57±2.06 1.45 9.794±0.0098 0.00 0.10 1.05 +0.05 230,84±0.87 0.61 9.777±0.0098-0.0093 0.1003 TABLE 14: CHANGE OF WAVELENGTH Wavelength Mean area ±SD SEM Assay % %Bias % RSD Original used level N= 3 220nm -5 579.42±5.35 3.783 99.94-0.022 0.923 225 225nm 0 521.39±0.690 0.487 100.05 0.008 0.132 230nm +5 498.69±2.91 2.057 100.63 0.199 0.585 International Journal of Pharmaceutical Sciences and Research 2349
LOD and LOQ: LOD and LOQ for losartan potassium were evaluated by injecting a series of solutions and diluted with known concentrations based on the peak response and the slope of the regression equation of the parameters of LOD and LOQ were decided. The LOD of drug noticed as 0.608µg/ml and LOQ was found 1.843µg/ml. By adopting the following formula LOD=3.3(SD)/S and LOQ = 10(SD)/S, where SD = standard deviation of response and S= slope of the calibration curve were computed. Comparison with the reported UV spectrophotometric method: The results obtained above were compared with that obtained from the reported HPLC method confirming similar accuracy and precision in the determination of losartan potassium by both methods Table 8 5. TABLE 15: ASSAY RESULTS OF LOSARTAN POTASSIUM Method Dosage form Declared value mg Found value RSD Recovery mg ±SD * Reference LOSACAR 50 50.13±0.026 0.064 100.26 ZYLTAN 50 50.07±0.0.024 0.061 100.14 COZAL 50 49.99±.101 0.24 99.98 Proposed LOSACAR 50 50.15±0.104 0.25 100.3 ZYLTAN 50 49.99±0.106 0.26 99.98 COZAL 50 50.11±0.024 0.060 100.22 * Average of three determination DISCUSSION: The proposed method obeys linearity within the concentration range of 6.4 to 9.6µg/ml and coefficient correlation was found to be 0.999.The regression of the curve was Y=0.999x+0.215.The detection and quantization limit as LOD (K=3.3) and LOQ (K=10) were calculated and the these were found to be0.608µg/ml and 1.843µg/ml respectively. The precision measurement of intra-day and inter-day with percent relative standard deviation, 0.44% and 0.43%, which indicated that the method is highly précised. The main reason of study precision is to establish that promoted RP-HPLC is accurate for analyzing losartan potassium in pharmaceutical formulation as well as bulk forms. The percentage recovery value Table 6, bout % indicates the accuracy of the method. No excipients present or interference in the analysis market formulation tablets. The result of analysis of dosage form obtained were good agreement with label claim. Losartan potassium was stale drug toward stress testing. CONCLUSION: The developed HPLC method is simple, precise, specific and accurate and the statistical analysis proved that method is reproducible and selective for the analysis of Losartan potassium in tablet dosage form. REFERENCES: 1. K. E. McCarthy, Q. Wang, E. W. Tsai, R. E. Gilbert, D. P. Ip, and M. A. Brooks, Determination of losartan and its degradates in COZAAR tablets by reversed-phase highperformance thin-layer chromatography, Journal of Pharmaceutical and Biomedical Analysis, vol. 17, no. 4-5, pp. 671 677, 1998 2. Breda C.A., Breda m., Frigerio E., Bioanalytical method validation: a risk based approach, Journal of pharmaceutical and biomedical analysis2004; 35: 887-89. 3. Wayne W D, Biostatistics: Analysis in health Science, 5 th Ed, John Wiley& Sons, New York, 1991. 4. International Conference on Harmonization of Technical requirement for registration of pharmaceuticals for human Use (ICH), (2005).Validation of Analytical procedures: Text and Methodology Q2 (R1). 5. U.S.pharmacopoeia: National formulary. 2015; 38 How to cite this article: Amna Mohammed BWE and Rudwan EH: RP-HPLC Method Development and Validation of Stability Indicating Method a for Estimation of Losartan Potassium under Stress Condition and Tablet Dosage Form. Int J Pharm Sci Res 2016; 7(6): 2343-51.doi: 10.13040/IJPSR.0975-8232.7(6).2343-51. All 2013 are reserved by International Journal of Pharmaceutical Sciences and Research. This Journal licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. This article can be downloaded to ANDROID OS based mobile. Scan QR Code using Code/Bar Scanner from your mobile. (Scanners are available on Google Playstore) International Journal of Pharmaceutical Sciences and Research 2350